Peroxyformic acid compositions for membrane filtration cleaning in energy services

ABSTRACT

Peroxyformic acid compositions for treatment and removal of biofilm growth and mineral deposits on membranes for energy services applications are disclosed. In particular, peroxyformic acid compositions are generated in situ or on site generation for the reduction and prevention, of biofilms and the mitigation of mineral buildup on the membranes. The compositions according to the invention are compatible with the membranes under application of use conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Non-Provisional application claiming priority to U.S. Ser. No.62/434,981 filed Dec. 15, 2016, herein incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The invention relates to use of peroxyformic acid compositions forremoval of biofilm growth and mineral deposits on membranes.Accordingly, the present invention relates to the field of membraneseparation processes and clean in place or wash composition for cleaningsuch membranes, including removal of minerals and biofilms through theuse of an antimicrobial wash. In particular, peroxyformic acidcompositions are generated in situ or by on site generation for thereduction, removal and/or kill of biofilms and the mitigation of mineralbuildup on the membranes. The compositions according to the inventionare unexpectedly compatible with the membranes under application of useconditions.

BACKGROUND OF THE INVENTION

Various technologies use membranes, including those membranes that applyreverse osmosis. A disadvantage in the use of membranes is that duringoperation, the membranes gradually become fouled. In particular, biofilmgrowth and mineral deposits on membranes, including reverse osmosismembranes, nanofiltration membranes, ultrafiltration membranes, andmicrofiltration membranes, can have detrimental results. Such biofilmgrowth and mineral deposits can cause severe flux declines, increasedpressure, reduced production, can negatively impact the quality offinished goods, and often results in premature replacement of suchmembranes.

Membranes provided within a separation facility can be treated usingclean-in-place (CIP) methods to provide flushing, rinsing, pretreatment,cleaning, and preserving, as filtration membranes have a tendency tofoul during processing. Fouling manifests itself as a decline in fluxand an increase in pressures with time of operation leading to decreasedproduction. Flux decline is typically a reduction in permeation flow orpermeation rates that occurs when all operating parameters, such aspressure, feed flow rate, temperature, and feed concentration are keptconstant. In general, membrane fouling is a complicated process and isbelieved to occur due to a number of factors including electrostaticattraction, hydrophobic and hydrophilic interactions, the deposition andaccumulation of feed components, e.g., suspended particulates,impermeable dissolved solutes, and even normally permeable solutes, onthe membrane surface and/or within the pores of the membrane. It isexpected that almost all feed components will foul membranes to acertain extent. See Munir Cheryan, Ultrafiltration and MicrofiltrationHandbook, Technical Publication, Lancaster, Pa., 1998 (Pages 237-288).Fouling components and deposits can include inorganic salts,particulates, microbials and organics.

Filtration membranes typically require periodic cleaning to allow forsuccessful industrial application within separation facilities such asthose found in the food, dairy, beverage and energy industries. Thefiltration membranes can be cleaned by removing foreign material fromthe surface and body of the membrane and associated equipment. Thecleaning procedure for filtration membranes can involve a clean-in-placeCIP process or in situ cleaning where cleaning agents are circulatedover and through the membrane to wet, soak, penetrate, dissolve and/orrinse away foreign materials from the membrane. Various parameters thatcan be manipulated for cleaning typically include time, temperature,mechanical energy, chemical composition, chemical concentration, soiltype, water type, hydraulic design, and membrane materials ofconstruction.

Conventional cleaning techniques include the use of high heat and/orextreme pH, i.e., very high alkalinity use solutions, or very low pHacidic use solutions. However, many surfaces cannot tolerate suchconditions. For example, membranes used in the energy services industryoften have specific limitations with respect to the temperature and pHat which they can be operated and cleaned due to the material from whichthey are constructed.

In general, the frequency of cleaning and type of chemical treatmentperformed on the membrane has been found to affect the operating life ofa membrane. It is believed that the operating life of a membrane can bedecreased as a result of chemical degradation of the membrane over time.Various membranes are provided having temperature, pH, and chemicalrestrictions to minimize degradation of the membrane material. Forexample, many polyamide reverse osmosis membranes have chlorinerestrictions because chlorine can have a tendency to halogenate anddamage the membrane. Cleaning and sanitizing filtration membranes isdesirable in order to comply with laws and regulations that may requirecleaning in certain applications (e.g., oil and gas production), reducemicroorganisms to prevent contamination of the product streams, andoptimize the process by restoring flux (and pressure).

Both oxidizing and non-oxidizing biocides are conventionally used incombination with alkaline treatments for disinfection of a membrane andto prevent or reduce the fouling of the membrane. Exemplary oxidizingagents are chloric compounds, which are known to have stronganti-microbial effects, however they have a significant disadvantage inthat they may damage the membrane surface. Such contact with membranesurfaces is a required part of the disinfectant process using theoxidizing biocide. Other exemplary techniques for cleaning membranes aredisclosed by U.S. Pat. No. 4,740,308 to Fremont et al.; U.S. Pat. No.6,387,189 to Groschl et al.; and U.S. Pat. No. 6,071,356 to Olsen; andU.S. Publication No. 2009/0200234.

Various methods of cleaning membranes are known to decrease the lifespanof a membrane as a result of damaging the membranes and surroundingequipment that is to be cleaned. For example, an acid treatment mighthave a corrosive effect on the surfaces of process equipment and onfiltration membranes used therein. Also, the rather high temperaturerequired entails an increase in energy costs. Furthermore, the use oflarge volumes of acidic inactivation compositions requires theirneutralization and proper disposal of the liquid waste. These and otherknown disadvantages of membrane cleaning systems are known.

In the context of energy services, there are additional concernsregarding water sources and the compatibility of these with theperoxyformic acid compositions of the invention for cleaning membranes.In an aspect, in the context of offshore oil and gas facilities thereare concerns regarding the water sources available, namely sea water,brine water, brackish water and produced water. The additional presenceof ions such as chloride, divalent metals and sulfate can further damagethe membrane and present issues in terms of compatibility of treatmentand cleaning protocols with the membrane material. Further, the complexdiversity of the species of microbes present in these waters can lead toan increase in biological fouling and the accumulation of biofilm onmembrane surfaces. These are exemplary concerns uniquely present in thetreatment of membranes for energy services applications. These concernsillustrate the need for membranes to separate out many species in seawater and other conditions used in oil and gas platforms. In particular,it is a need to use membranes to separate out sulfate from seawater inan oil and gas open sea platform.

Although various agents preventing microbial growth, such as oxidizers,have been used for membrane cleaning there is still a need for animproved method for the prevention of microbial growth and biofilmformation on membranes.

Accordingly, it is an objective of the claimed invention to provideperoxyformic acid compositions generated in situ for the prevention ofmineral scale formation, deposit build up and removal of microbialgrowth on membranes and biofouling of membranes. In particular, it is anobject of the invention to provide a method, which does not damage themembranes and which mitigates microbial growth and biofouling on themembranes.

A further object of the invention is to replace2,2-dibromo-3-nitrilopropionamide (DBNPA), a traditional biocide thathydrolyzes under both acidic and alkaline conditions, with theperoxyformic acid compositions according to the invention.

A further object of the invention is to provide a membrane-compatiblecomposition, such that the composition does not contain any componentsdestroying or blocking the membrane, and/or generate chlorine speciescausing damage to membranes.

Other objects, advantages and features of the present invention willbecome apparent from the following specification taken in conjunctionwith the accompanying drawings.

BRIEF SUMMARY OF THE INVENTION

An advantage of the invention is a membrane compatible peroxycarboxylicacid composition comprising peroxyformic acid composition generated insitu or on site for use to remove and/or reduce biofilm growth andmineral deposits on membranes. It is an advantage of the presentinvention that the cleaning compositions are biodegradable, decomposeinto non-hazardous products, which therefore leave no toxic traces onthe treated membranes (due to rapid degradation into water, carbondioxide and formic acid which are recognized as GRAS) and do notnegatively interfere with the membranes. Moreover, the peroxyformic acidcomposition is suitable for generation in situ or on site of a point ofuse, allowing a user to promptly apply the composition to a membrane inneed of treatment to contact the membrane surface and control biofilmgrowth at the place where the biofilm bacteria adhere and initiatebiofilm formation.

In an embodiment, the present invention discloses onsite generatedperoxycarboxylic acid compositions comprising compositions of performicacid and/or combinations of performic acid and additional peracidsand/or oxidizing chemistries that efficiently kill and removal biofilmsand other soils, along with inorganic scale on membranes withoutdamaging or negatively interfering with the membranes treated.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation showing the average log reductionof P. aeruginosa biofilm after exposure to the peroxyformic acidformulations according to an embodiment of the invention.

FIG. 2 shows the average log reduction of mesophilic spores afterexposure to the peroxyformic acid formulations according to anembodiment of the invention.

FIG. 3 shows membrane compatibility assessment of reverse osmosismembranes using a peroxyformic acid formulation according to anembodiment of the invention compared to commercially available peracidcomposition.

FIG. 4 shows membrane compatibility assessment via clean water fluxmeasurements of reverse osmosis membranes using a peroxyformic acidformulation according to an embodiment of the invention compared tocommercially available chemical control compositions.

FIG. 5 shows membrane compatibility assessment via salt rejectionmeasurements of reverse osmosis membranes using a peroxyformic acidformulation according to an embodiment of the invention compared tocommercially available chemical control compositions.

FIG. 6 shows the results of statistical analysis on volume of biofilmperformed on oil and gas biofilm grown before and after treatment withperoxyformic acid

FIG. 7 shows the results of the DPD assay described in Example 7.Notably, the example utilizing salt water (SW) does not substantiallyincrease the presence of free chlorine as compared to fresh water (FW)

FIG. 8 shows the results of the DPD assay described in Example 7.Notably, the present invention results in a substantially lower freechlorine composition in comparison with DBNPA.

Various embodiments of the present invention will be described in detailwith reference to the drawings, wherein like reference numeralsrepresent like parts throughout the several views. Reference to variousembodiments does not limit the scope of the invention. Figuresrepresented herein are not limitations to the various embodimentsaccording to the invention and are presented for exemplary illustrationof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to membrane compatible peroxycarboxylicacid composition comprising peroxyformic acid composition generated insitu or on site for use to reduce and/or prevent biofilm growth andmineral deposits on membranes. The embodiments of this invention are notlimited to particular peroxyformic acid compositions, which can vary andare understood by skilled artisans based on the disclosure herein of thepresent invention. It is further to be understood that all terminologyused herein is for the purpose of describing particular embodimentsonly, and is not intended to be limiting in any manner or scope. Forexample, as used in this specification and the appended claims, thesingular forms “a,” “an” and “the” can include plural referents unlessthe content clearly indicates otherwise. Further, all units, prefixes,and symbols may be denoted in its SI accepted form.

Numeric ranges recited within the specification are inclusive of thenumbers within the defined range. Throughout this disclosure, variousaspects of this invention are presented in a range format. It should beunderstood that the description in range format is merely forconvenience and brevity and should not be construed as an inflexiblelimitation on the scope of the invention. Accordingly, the descriptionof a range should be considered to have specifically disclosed all thepossible sub-ranges as well as individual numerical values within thatrange (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

So that the present invention may be more readily understood, certainterms are first defined. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which embodiments ofthe invention pertain. Many methods and materials similar, modified, orequivalent to those described herein can be used in the practice of theembodiments of the present invention without undue experimentation, thepreferred materials and methods are described herein. In describing andclaiming the embodiments of the present invention, the followingterminology will be used in accordance with the definitions set outbelow.

The term “about,” as used herein, refers to variation in the numericalquantity that can occur, for example, through typical measuring andliquid handling procedures used for making concentrates or use solutionsin the real world; through inadvertent error in these procedures;through differences in the manufacture, source, or purity of theingredients used to make the compositions or carry out the methods; andthe like. The term “about” also encompasses amounts that differ due todifferent equilibrium conditions for a composition resulting from aparticular initial mixture. Whether or not modified by the term “about”,the claims include equivalents to the quantities.

The term “actives” or “percent actives” or “percent by weight actives”or “actives concentration” are used interchangeably herein and refers tothe concentration of those ingredients involved in cleaning expressed asa percentage minus inert ingredients such as water or salts. Theexamples embodied in the application may refer to composition or productconcentrations as opposed to the actives concentration of theperoxyformic acid as will be readily understood by those skilled in theart by the description thereof.

As used herein, the term “alkyl” or “alkyl groups” refers to saturatedhydrocarbons having one or more carbon atoms, including straight-chainalkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, nonyl, decyl, etc.), cyclic alkyl groups (or “cycloalkyl” or“alicyclic” or “carbocyclic” groups) (e.g., cyclopropyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl, etc.), branched-chain alkyl groups(e.g., isopropyl, tert-butyl, sec-butyl, isobutyl, etc.), andalkyl-substituted alkyl groups (e.g., alkyl-substituted cycloalkylgroups and cycloalkyl-substituted alkyl groups).

Unless otherwise specified, the term “alkyl” includes both“unsubstituted alkyls” and “substituted alkyls.” As used herein, theterm “substituted alkyls” refers to alkyl groups having substituentsreplacing one or more hydrogens on one or more carbons of thehydrocarbon backbone. Such substituents may include, for example,alkenyl, alkynyl, halogeno, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxy, aryloxycarbonyloxy, carboxylate,alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl,alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl,phosphate, phosphonato, phosphinato, cyano, amino (including alkylamino, dialkylamino, arylamino, diarylamino, and alkylarylamino),acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyland ureido), imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, alkylsulfinyl, sulfonates, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclic, alkylaryl, or aromatic(including heteroaromatic) groups.

In some embodiments, substituted alkyls can include a heterocyclicgroup. As used herein, the term “heterocyclic group” includes closedring structures analogous to carbocyclic groups in which one or more ofthe carbon atoms in the ring is an element other than carbon, forexample, nitrogen, sulfur or oxygen. Heterocyclic groups may besaturated or unsaturated. Exemplary heterocyclic groups include, but arenot limited to, aziridine, ethylene oxide (epoxides, oxiranes), thiirane(episulfides), dioxirane, azetidine, oxetane, thietane, dioxetane,dithietane, dithiete, azolidine, pyrrolidine, pyrroline, oxolane,dihydrofuran, and furan.

As used herein, the term “cleaning” refers to a method used tofacilitate or aid in soil removal, bleaching, microbial populationreduction, and any combination thereof. As used herein, the term“microorganism” refers to any noncellular or unicellular (includingcolonial) organism. Microorganisms include all prokaryotes.Microorganisms include bacteria (including cyanobacteria), spores,lichens, fungi, protozoa, virinos, viroids, viruses, phages, and somealgae. As used herein, the term “microbe” is synonymous withmicroorganism.

As used herein, the term “disinfectant” refers to an agent that killsall vegetative cells including most recognized pathogenicmicroorganisms, using the procedure described in A.O.A.C. Use DilutionMethods, Official Methods of Analysis of the Association of OfficialAnalytical Chemists, paragraph 955.14 and applicable sections, 15thEdition, 1990 (EPA Guideline 91-2). As used herein, the term “high leveldisinfection” or “high level disinfectant” refers to a compound orcomposition that kills substantially all organisms, except high levelsof bacterial spores. As used herein, the term “intermediate-leveldisinfection” or “intermediate level disinfectant” refers to a compoundor composition that kills mycobacteria, most viruses, and bacteria witha chemical germicide registered as a tuberculocide by the EnvironmentalProtection Agency (EPA). As used herein, the term “low-leveldisinfection” or “low level disinfectant” refers to a compound orcomposition that kills some viruses and bacteria with a chemicalgermicide registered as a hospital disinfectant by the EPA.

The term “hard surface” refers to a solid, substantially non-flexiblesurface such as a counter top, tile, floor, wall, panel, window,plumbing fixture, kitchen and bathroom furniture, appliance, engine,circuit board, and dish. Hard surfaces may include for example, healthcare surfaces and food processing surfaces.

The term “incompatibility,” as used herein refers to conditions orscenarios in which the chemical nature of the material being filtered isnot compatible with the structure of the membrane. Incompatibility ofmaterials can be detrimental to the membrane and lead to reduction infiltration capability, damage to the membrane, complete failure of themembrane, etc. As referred to herein a treatment composition and methodthat is membrane “compatible” does not cause significant reduction infiltration capability as a result of physical damage to the membrane,which can be measured by a decrease in flux of the membrane beyond thetypical flux of a new membrane or a significant decrease in rejection,for example decrease in a monovalent salt in RO permeate, divalent saltin NF permeate, etc. In an aspect, a reduction in filtration capabilityof more than 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or more isindicative of incompatibility.

As one skilled in the art shall ascertain, the flux and salt rejectionlimits for a membrane are specifications supplied by a membranemanufacturer as they can vary with manufacture of the membrane.Accordingly, a treatment composition and method that is membrane“compatible” complies with the supplier specification for the membranewithout causing reduction in filtration capability as a result ofphysical damage to the membrane. In an exemplary embodiment, sulfaterejection membranes (SRU, Sulfate Reduction Unit), the flux can increasewith damage or decrease with scale and biofilm contamination but arelative decrease in sulfate salt rejection (i.e. more salt found in thepermeate flow), is the primary criteria on efficacy of the system.

The term “membrane” means a structure having lateral dimensions muchgreater than its thickness though which a mass transfer may occur,membranes may be used to filter liquids.

As used herein, the terms “mixed” or “mixture” when used relating to“percarboxylic acid composition,” “percarboxylic acids,”“peroxycarboxylic acid composition” or “peroxycarboxylic acids” refer toa composition or mixture including more than one percarboxylic acid orperoxycarboxylic acid

For the purpose of this patent application, successful microbialreduction is achieved when the microbial populations are reduced by atleast about 50%, or by significantly more than is achieved by a washwith water. Larger reductions in microbial population provide greaterlevels of protection.

As used herein the term “microbial control” refers to an agent thatreduces the number of bacterial contaminants to safe levels as judged bythe environmental protection agency. In an embodiment, microbial controlagents for use in this invention will provide a microbial reductionequivalent to at least a 1 log and more preferably a reductionequivalent to 3-log order reduction.

As used herein, the term “sanitizer” refers to an agent that reduces thenumber of bacterial contaminants to safe levels as judged by publichealth requirements. In an embodiment, sanitizers for use in thisinvention will provide at least a 3 log reduction and more preferably a5-log order reduction. These reductions can be evaluated using aprocedure set out in Germicidal and Detergent Sanitizing Action ofDisinfectants, Official Methods of Analysis of the Association ofOfficial Analytical Chemists, paragraph 960.09 and applicable sections,15th Edition, 1990 (EPA Guideline 91-2). According to this reference asanitizer should provide a 99.999% reduction (5-log order reduction)within 30 seconds at room temperature, 25±2° C., against several testorganisms.

As used herein, the term “soil” or “stain” refers to a polar-oilyhydrocarbon or a non-polar oily substance which may or may not containparticulate matter such as mineral clays, sand, natural mineral matter,carbon black, graphite, kaolin, environmental dust, etc.

As used in this invention, the term “sporicide” refers to a physical orchemical agent or process having the ability to cause greater than a 90%reduction (1-log order reduction) in the population of spores ofBacillus cereus or Bacillus subtilis within 10 seconds at 60° C. Incertain embodiments, the sporicidal compositions of the inventionprovide greater than a 99% reduction (2-log order reduction), greaterthan a 99.99% reduction (4-log order reduction), or greater than a99.999% reduction (5-log order reduction) in such population within 10seconds at 60° C.

Differentiation of antimicrobial “-cidal” or “-static” activity, thedefinitions which describe the degree of efficacy, and the officiallaboratory protocols for measuring this efficacy are considerations forunderstanding the relevance of antimicrobial agents and compositions.Antimicrobial compositions can affect two kinds of microbial celldamage. The first is a lethal, irreversible action resulting in completemicrobial cell destruction or incapacitation. The second type of celldamage is reversible, such that if the organism is rendered free of theagent, it can again multiply. The former is termed microbiocidal and thelater, microbistatic. A sanitizer and a disinfectant are, by definition,agents which provide antimicrobial or microbiocidal activity. Incontrast, a preservative is generally described as an inhibitor ormicrobistatic composition

The term “substantially similar cleaning performance” refers generallyto achievement by a substitute cleaning product or substitute cleaningsystem of generally the same degree (or at least not a significantlylesser degree) of cleanliness or with generally the same expenditure (orat least not a significantly lesser expenditure) of effort, or both.

As used herein, the term “sulfoperoxycarboxylic acid,” “sulfonatedperacid,” or “sulfonated peroxycarboxylic acid” refers to theperoxycarboxylic acid form of a sulfonated carboxylic acid. In someembodiments, the sulfonated peracids of the present invention aremid-chain sulfonated peracids. As used herein, the term “mid-chainsulfonated peracid” refers to a peracid compound that includes asulfonate group attached to a carbon that is at least one carbon (e.g.,the three position or further) from the carbon of the percarboxylic acidgroup in the carbon backbone of the percarboxylic acid chain, whereinthe at least one carbon is not in the terminal position. As used herein,the term “terminal position,” refers to the carbon on the carbonbackbone chain of a percarboxylic acid that is furthest from thepercarboxyl group.

The term “threshold agent” refers to a compound that inhibitscrystallization of water hardness ions from solution, but that need notform a specific complex with the water hardness ion. Threshold agentsinclude but are not limited to a polyacrylate, a polymethacrylate, anolefin/maleic copolymer, and the like.

As used herein, the term “waters” includes fresh water, sea water,produced water, brackish water and water used in oil and gas productionsystems, or transport waters. Transport waters include e.g., as found influmes, pipe transports, water stored in pipelines, tanks or other waterholding containers, and the like. The term “weight percent,” “wt-%,”“percent by weight,” “% by weight,” and variations thereof, as usedherein, refer to the concentration of a substance as the weight of thatsubstance divided by the total weight of the composition and multipliedby 100. It is understood that, as used here, “percent,” “%,” and thelike are intended to be synonymous with “weight percent,” “wt-%,” etc.The, the term PPM refers to parts per million.

The methods, systems, apparatuses, and compositions of the presentinvention may comprise, consist essentially of, or consist of thecomponents and ingredients of the present invention as well as otheringredients described herein. As used herein, “consisting essentiallyof” means that the methods, systems, apparatuses and compositions mayinclude additional steps, components or ingredients, but only if theadditional steps, components or ingredients do not materially alter thebasic and novel characteristics of the claimed methods, systems,apparatuses, and compositions.

Methods of Cleaning Membranes

The present invention comprises peroxyformic acid compositions which canbe used as a cleaning composition, namely an antimicrobial cleaningcomposition, a booster or as part of an alkaline, acid and/or enzymaticcleaning composition, a combination of other peroxy acid and/oroxidizing compositions, and methods of use of the same. As referred toherein, the removing of microorganisms, biofilm and mineral depositsrefers to the reduction in microorganisms, biofilm and mineral depositson a membrane surface, the disbursement of microorganisms, biofilm andmineral deposits on a membrane surface, and/or the inactivating ofmicroorganisms, biofilm and mineral deposits on a membrane surface.

In an aspect, the peroxyformic acid compositions are applied to orcontact a membrane in need of removing microbial growth and mineraldeposits. Membranes are utilized for a variety of separation methods toconvert a mixture of a substance(s) into distinct mixtures, at least oneof which is enriched in one or more of the mixture's constituents. Themembranes that can be treated according to the invention include anymembranes that are designed for periodic cleaning, and are oftenutilized in various applications requiring separation by filtration.Exemplary industries that utilize membranes that can be treatedaccording to the invention include the energy industry. Energy industryuses membranes for desalination, sulfate removal and contaminantremoval. Additional uses include reverse osmosis (RO) desalinationapplications.

Membranes that can be treated according to the invention include thoseprovided in the form of spiral wound membranes, plate and framemembranes, tubular membranes, capillary membranes, hollow fibermembranes and the like. In the case of spiral wound membranes, it isexpected that the industrial commonly available diameters of 3.8 inch,6.2 inch, and 8.0 inch can be treated using the methods of the presentinvention. The membranes can be generally characterized according to thesize of the particles being filtered. Four common types of membranetypes include microfiltration (MF) membranes, ultrafiltration (UF)membranes, nanofiltration (NF) membranes, and reverse osmosis (RO)membranes.

In an aspect, microfiltration membranes are particularly suited fortreatment according to the invention, which employs a separation processin which particles and dissolved macromolecules larger than 0.1 μm donot pass through the membrane, and which may be pressure driven. In afurther aspect, microfiltration membranes may have a pore size rangefrom about 0.05 to about 1 μm. In a further aspect, microfiltrationmembranes target particular material and contaminants such as bacteriaand suspended solids.

In an aspect, ultrafiltration (UF) membranes are particularly suited fortreatment according to the invention. Ultrafiltration is a process offiltration in which hydrostatic pressure forces a filtrate liquidagainst a semipermeable membrane, suspended solids and solutes of highmolecular weight are retained, while water and low molecular weightsolutes pass through the membrane, it is used in industry and researchfor purifying and concentrating macromolecular (10³-10⁶ Da) solutions.It may be applied in cross-flow or dead-end mode and separation inultrafiltration may undergo concentration polarization. The exact metesand bounds and protocols for applying and categorizing ultrafiltrationare set forth in the scientific reference: Ultrafiltration andMicrofiltration Handbook, Second Edition, by Munir Cheryan, Published byCRC Press LLC, (1998), which is herein incorporated by reference. In afurther aspect, ultrafiltration membranes may have a pore size rangefrom about 0.005 to about 0.5 μm. In a further aspect, ultrafiltrationmembranes target particular material and contaminants such as bacteriaand suspended solids, plus humic acids and some viruses.

In an aspect, nanofiltration membranes are particularly suited fortreatment according to the invention, which employs a separation processin which particles and dissolved macromolecules larger than 1 nm do notpass through the membrane, and which may be pressure driven. In afurther aspect, nanofiltration membranes may have a pore size range fromabout 0.0005 to about 0.01 μm. In a further aspect, nanofiltrationmembranes target contaminants such as viruses, bacteria, and suspendedsolids and further target particular materials including dissolvedmetals and salts.

In an aspect, reverse osmosis (RO) membranes are particularly suited fortreatment according to the invention. Reverse osmosis is a waterpurification technology that uses a hydrostatic force (a thermodynamicparameter) to overcome osmotic pressure (a colligative property) in thewater to remove one or more unwanted items from the water, RO may be amembrane based separation process, wherein the osmotic pressure isovercome by the hydrostatic force, it may be driven by chemicalpotential, RO may be pressure driven, RO can remove many types ofmolecules and ions from solutions and is used in both industrialprocesses and in producing potable water, in a pressurized RO processthe solute is retained on the pressurized side of the membrane and thepure solvent is allowed to pass to the other side, to be “selective,” anRO membrane may be sized to not allow large molecules or ions throughthe pores (holes), and often only allows smaller components of thesolution (such as the solvent) to pass freely, in some cases dissolvedmolecules larger than 0.5 nm do not pass through membrane. In a furtheraspect, RO membranes may have a pore size range from about 0.0001 toabout 0.001 μm. In a further aspect, reverse osmosis membranes targetcontaminants such as monovalent ions, multivalent ions, viruses,bacteria, and suspended solids and further target particular materialsincluding smaller dissolved metals and salts.

Because of the pore sizes, each membrane process operates at an optimalpressure. Microfiltration membrane systems generally operate atpressures less than about 30 psig. Ultrafiltration membrane systemsgenerally operate at pressures of about 15-150 psig. Nanofiltrationmembrane systems generally operate at pressures of about 75-500 psig.Reverse osmosis membrane systems generally operate at pressures of about200-2000 psig. Membranes can be formed from a variety of materials thatare commonly used to form membranes including cellulose acetate,polyamide, polysulfone, vinylidene fluoride, acrylonitrile, stainlesssteel, ceramic, etc. These various membrane chemical types and othermaterials of construction may have specific pH, oxidant, solvent,chemical compatibility restrictions, and/or pressure limitations.

Membranes may comprise and/or consist of various polymeric components,including for example, cellulose, cellulose acetate, cellulosetri-acetate, nitrocellulose, polysulfone, polyethersulfone, fullyaromatic polyamide, polyvinylidene fluoride, polytetrafluoroethylene,polyacrylnitrile, polypropylene, carbon, an organic membrane materials,such as alpha-aluminum oxide or zirconium oxide, and may include notfurther specified backing material. Membranes may further or in thealternative comprise and/or consist of ceramic and stainless steel.Additional suitable materials are disclosed in U.S. Pat. No. 7,871,521,which is incorporated by reference in its entirety. The methods oftreating a membrane with the peroxyformic acid compositions can includea plurality of steps. A first step can be referred to as a productremoval step or displacement where product (e.g. whey, milk, etc.) isremoved from the filtration system. The product can be effectivelyrecovered and used as opposed to discharging as plant effluent. Ingeneral, the product removal step can be characterized as an exchangestep where water, gas, or multiple phase flow displaces the product fromthe membrane system. The product removal step can last as long as ittakes to remove and recover product from the filtration system. Ingeneral, it is expected that the product removal step will take at leasta couple minutes for most filtration systems.

The dosing of the peroxyformic acid compositions for contacting themembrane is for a sufficient amount of time to contact microorganismsand/or mineral deposits on the membrane. In an aspect, the peroxyformicacid compositions contacts the membrane for at least 15 minutes to 15hours, for at least 30 minutes to 10 hours, for at least 30 minutes to 5hours, for at least 30 minutes to 4 hours, or any range of time therebetween. In an aspect, the dosing of the peroxyformic acid (andoptionally other peroxy acids and/or oxidizing chemistries) at lowerconcentrations for treatment according to the invention is suitable fora longer contact time and further beneficially results in microbialreduction without causing damage to the membrane. In an aspect, theintermittent dosing of the peroxyformic acid compositions providescleaning at intervals which prevent the build up of microorganismsand/or mineral deposits on the membrane. The dosing can be provided on adaily, bi-weekly, weekly or other interval to ensure dosing at afrequency sufficient to prevent the build up of microorganisms and/ormineral deposits on the membrane.

In an aspect, the peroxyformic acid compositions contact the membranesin a use solution of from about 0.00001% to about 0.1% activeperoxyformic acid, from about 0.00005% to about 0.1% active peroxyformicacid, 0.0005% to about 0.1% active peroxyformic acid, 0.005% to about0.1% active peroxyformic acid, from about 0.01% to about 0.1% activeperoxyformic acid, or from about 0.025% to about 0.05% activeperoxyformic acid.

In an aspect, the peroxyformic acid compositions contact the membranesat an actives concentration from about 0.5 ppm to about 300 ppm, fromabout 0.5 ppm to about 200 ppm, from about 1 ppm to about 100 ppm, fromabout 50 ppm to about 100 ppm, or from about 70 ppm to about 100 ppmactive peroxyformic acid.

The peroxyformic acid and the membrane can be contacted to form atreated target composition comprising any suitable concentration of saidperoxyformic acid, e.g., at least about 1 ppm, at least about 10 ppm atleast about 100 ppm, or preferably from about 1-1,000 ppm ofperoxyformic acid. The composition used in the present methods canretain any suitable concentration or percentage of the peroxyformic acidactivity for any suitable time after the treated target composition isformed. In some embodiments, the composition used in the present methodsretains at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90% ofthe initial peroxyformic acid activity for any suitable time after thetreated target composition is formed. In other embodiments, thecomposition used in the present methods retains at least about 60% ofthe initial peroxyformic acid activity for at least 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30 minutes, 1 hour, or 2 hoursafter the treated target composition is formed.

In an aspect, the temperature of the membrane treatment may be betweenabout 4° C. to 60° C., between about 4° C. to 50° C., between about 4°C. to 40° C., or any range of there between. In an aspect, thetemperature of the membrane treatment may be ambient temperatures, suchas from 4° C. to 30° C. In a further aspect of the invention, andwithout wishing to be limited to a particular theory, the temperature ofthe membrane treatment is selected so as to provide desirable chemicalkinetics, avoid precipitation of compositions, and to account forgeographic and/or environmental concerns.

In an aspect, the pressure of the membrane treatment is selected so thatthe pressure drop from feed to concentrate is compensated for. In astill further aspect, the pressure is selected to that little to nopermeate is produced. In a further aspect, and without wishing to belimited to a particular theory, the pressure selected is low enough thatredeposition of dirt and/or other fouling material on the membrane isminimized. In an aspect, the feed pressure may be between about 20 psigand 60 psig.

Beneficially, the methods of treating the membrane do not negativelyinterfere with the compatibility of the membrane, as may be measured bythe flux through the membrane, i.e. the flow rate of water or a solutionprocessed through membrane. In a beneficial aspect, the method oftreating the membrane does not result in any negative impact onperformance, such as may be determined by flux, pressure or othermeasurements understood by those skilled in the art. Additionally, themethods of treating a membrane according to the present invention doesnot produce negative or detrimental chemical reactions, such as chlorinespecies, with the membrane material that would otherwise create chemicalincompatibility.

In an aspect, the peroxyformic acid can treat a membrane for periods ofat least one year, at least two years, or at least three years withoutdamaging the membrane surface in a way that interferes with flow.

In an aspect of the invention, the methods of treating the membrane witha peroxyformic acid composition replace the need for or reduce theamount of the conventional biocide employed in energy servicesapplications, namely 2,2-dibromo-3-nitrilopropionamide (DBNPA). Theperoxyformic acid composition used in place of the DBNPA or otherconventional biocides beneficially removes the need to hold treatedwater in a sump or other retention step in order to treat the waterbefore it is overboarded in off-shore applications of use. The use ofperoxyformic acid compositions does not require further treatment and/ortime to remove the biocide due to the short half-life of theperoxyformic acid.

The methods of treating the membranes according to the invention providebroad antimicrobial efficacy. In a particular aspect, the methods oftreating the membranes according to the invention provide biofilmantimicrobial and biocidal efficacy. Exemplary microorganismssusceptible to the peracid compositions of the invention include, grampositive bacteria (e.g., Staphylococcus aureus, Bacillus species (sp.)like Bacillus subtilis, Clostridia sp.), gram negative bacteria (e.g.,Escherichia coli, Pseudomonas sp., Klebsiella pneumoniae, Legionellapneumophila, Enterobacter sp., Serratia sp., Desulfovibrio sp., andDesulfotomaculum sp. Desulfovibio sp.), planktonic microbes, sessilemicrobes, yeasts (e.g., Saccharomyces cerevisiae and Candida albicans),molds (e.g., Aspergillus niger, Cephalosporium acremonium, Penicilliumnotatum, and Aureobasidium pullulans), filamentous fungi (e.g.,Aspergillus niger and Cladosporium resinae), algae (e.g., Chlorellavulgaris, Euglena gracilis, and Selenastrum capricornutum), and otheranalogous microorganisms and unicellular organisms (e.g., phytoplanktonand protozoa). Other exemplary microorganisms susceptible to the peracidcompositions of the invention include the exemplary microorganismsdisclosed in U.S. patent application US 2010/0160449, e.g., the sulfur-or sulfate-reducing bacteria, such as Desulfovibrio and Desulfotomaculumspecies.

The methods of treating the membranes according to the invention providemineral scale removal and removal of mineral buildup conventionallyfound on membranes. In a particular aspects, the methods of treating themembranes according to the invention provide scale and mineral removaland prevention of buildup or accumulation. Mineral scales are solublesalts that precipitate out as crystalline mineral scales within asystem, such as filtration systems employing membranes. Examples ofmineral scales include calcium carbonate, calcium sulfate, calciumphosphate, barium sulfate, strontium sulfate, iron hydroxide, ironsulfide, silicone dioxide (silica), calcium oxalate, etc.

Another step often used can be referred to as a pre-rinse step. Ingeneral, water and/or an alkaline solution can be run through thefiltration system to remove soils. It should be understood that alarge-scale filtration system refers to an industrial system having atleast about 10 membrane vessels, at least about 40 membranes, and atotal membrane area of at least about 200 m². Industrial filtrationsystems for use in dairy and brewery applications often include about 10to about 200 membrane vessels, about 40 to about 1,000 membranes, and atotal membrane area of about 200 m² to about 10,000 m².

In an aspect, the methods of treating the membrane with the peroxyformicacid compositions can further comprise additional treatment cyclesincluding an acidic treatment, an alkaline treatment, an enzymatictreatment and/or a neutral treatment either before or after theperoxyformic acid composition contacts the membrane.

In an alternative aspect, the methods of treating the membrane with theperoxyformic acid compositions can exclude any additional treatmentcycles including an acidic treatment, an alkaline treatment, anenzymatic treatment and/or a neutral treatment either before or afterthe peroxyformic acid composition contacts the membrane.

In an aspect, an alkaline treatment employs an alkaline use solution tocontact the membrane at the same time, and/or before, and/or after theperoxyformic acid composition has been applied to the surface. Exemplaryalkaline sources suitable for use with the methods of the presentinvention include, but are not limited to, basic salts, amines, alkanolamines, carbonates and silicates. Other exemplary alkaline sources foruse with the methods of the present invention include NaOH (sodiumhydroxide), KOH (potassium hydroxide), TEA (triethanol amine), DEA(diethanol amine), MEA (monoethanolamine), sodium carbonate, andmorpholine, sodium metasilicate and potassium silicate. The alkalinesource selected is compatible with the surface to be cleaned. In someembodiments, the alkaline override use solution includes an activatorcomplex. In other embodiments, an activator complex is applied to thesurface prior to the application of an alkaline override use solution.The alkaline override use solution selected is dependent on a variety offactors, including, but not limited to, the type of soil to be removed,and the surface from which the soil is removed.

In an aspect, an acidic treatment employs an acidic use solution tocontact the membrane at the same time, and/or before, and/or after theperoxyformic acid composition has been applied to the surface. Exemplaryacid sources suitable for use with the methods of the present inventioninclude, but are not limited to, mineral acids (e.g., phosphoric acid,nitric acid, sulfuric acid) and organic acids (e.g., lactic acid, aceticacid, hydroxyacetic acid, citric acid, glutamic acid, glutaric acid,methane sulfonic acid, acid phosphonates (e.g., HEDP), and gluconicacid). In some embodiments, the ideal additional acidic componentprovides good chelation once neutralized by the alkaline override usesolution.

In some embodiments, the additional acidic component present in theactive oxygen use solution includes a carboxylic acid. Generally,carboxylic acids have the formula R—COOH wherein the R may represent anynumber of different groups including aliphatic groups, alicyclic groups,aromatic groups, heterocyclic groups, all of which may be saturated orunsaturated as well as substituted or unsubstituted. Carboxylic acidsfor use with the methods of the present invention may include thosehaving one, two, three, or more carboxyl groups.

In an aspect, membranes treated with the peroxyformic acid compositionsaccording to the invention do not decrease the lifespan of the membranein comparison to a membrane treated with a conventional acidic andalkaline cleaning process. In an aspect, membranes treated according tothe invention are suitable for use for at least 6 months to a year, atleast 6 months, at least 7 months, at least 8 months, at least 9 months,at least 10 months, at least 11 months, at least 12 months, at least 13months, at least 14 months, at least 15 months, at least 16 months, atleast 17 months, at least 18 months, at least 19 months, at least 20months, at least 21 months, at least 22 months, at least 23 months, orat least 24 months. One skilled in the art ascertains that the lifespanof a membrane is impacted by various factors including process methods,pressure, pH, temperature, etc.

Membrane Filtration Cleaning Compositions

In one aspect, the present invention employs peroxyformic acidcompositions produced in situ or at a point of use for the treatment ofmembranes according to the invention comprising contacting formic acidwith hydrogen peroxide to form a resulting aqueous composition thatcomprises a peracid that comprises peroxyformic acid, wherein beforesaid contacting, the ratio between the concentration of said formic acid(w/v) and the concentration of said hydrogen peroxide (w/v) is about 2or higher, and the ratio between the concentration of said peracid (w/w)and the concentration of hydrogen peroxide (w/w) in said formedresulting aqueous composition reaches about 2 or higher withinpreferably about 1 hour, or preferably within about 10 minutes of saidcontacting.

In a further aspect, the present invention employs a combination ofacids produced in situ or at the point of use for the treatment ofmembranes according to the invention. In one embodiment of theinvention, the combination of acids comprises for example, formic acidand acetic acid, which is then contacted with hydrogen peroxide to forma resulting aqueous composition that comprises a peracid compositionthat comprises peroxyformic acid and peroxyacetic acid, wherein theratio between the concentration of said formic acid and acetic acid andthe concentration of said hydrogen peroxide (w/v) is about 2 or higher,and the ratio between the concentration of said peracid (w/w) and theconcentration of hydrogen peroxide (w/w) in said formed resultingaqueous composition reaches about 2 or higher within preferably about 1hour, or preferably within about 10 minutes of said contacting.

The formic acid used in the present methods can be provided in anysuitable way. In some embodiments, before the contacting step, theformic acid can be provided in a composition that comprises formic acid,e.g., an aqueous solution that comprises formic acid. In otherembodiments, before the contacting step, the formic acid can be providedin a composition that comprises a substance that generates formic acidupon contact with an aqueous composition. Any suitable substance thatgenerates formic acid can be used in the present methods. The substancecan be a salt of formate, e.g., a sodium or ammonium salt of formate, oran ester of formate. Exemplary esters of formate include glycerolformates, ethylene glycol formates, pentaerythritol formates, mannitolformates, propylene glycol formates, sorbitol formates and sugarformates. Exemplary sugar formates include sucrose formates, dextrinformates, maltodextrin formates, and starch formates. In someembodiments the formates may be provided in a solid composition, such asa starch formate.

The hydrogen peroxide used in the present methods can be provided in anysuitable way. In some embodiments, before the contacting step, thehydrogen peroxide can be provided in a composition that compriseshydrogen peroxide, e.g., an aqueous solution that comprises hydrogenperoxide. In other embodiments, before the contacting step, the hydrogenperoxide can be provided in a composition that comprises a substancethat generates hydrogen peroxide upon contact with an aqueouscomposition. Any suitable substance that generates hydrogen peroxide canbe sued in the present methods. The substance can comprise a precursorof hydrogen peroxide. Any suitable precursor of hydrogen peroxide can beused in the present methods. For example, the precursor of hydrogenperoxide can be sodium percarbonate, sodium perborate, urea hydrogenperoxide, or PVP-hydrogen peroxide.

In some embodiments, formic acid provided in a first aqueous compositionis contacted with hydrogen peroxide provided in a second aqueouscomposition to form peroxyformic acid and/or mixed peroxyacids and/oracids in the resulting aqueous composition. In other embodiments, formicacid provided in a first aqueous composition is contacted with asubstance that generates hydrogen peroxide upon contact with an aqueouscomposition provided in a second solid composition to form peroxyformicacid in the resulting aqueous composition. In still other embodiments, asubstance that generates formic acid upon contact with an aqueouscomposition provided in a first solid composition is contacted withhydrogen peroxide provided in a second aqueous composition to formperoxyformic acid in the resulting aqueous composition. In yet otherembodiments, a substance that generates formic acid upon contact with anaqueous composition provided in a first solid composition and asubstance that generates hydrogen peroxide upon contact with an aqueouscomposition provided in a second solid composition are contacted with athird aqueous composition to form peroxyformic acid in the resultingaqueous composition. In yet other embodiments, a substance thatgenerates formic acid upon contact with an aqueous composition and asubstance that generates hydrogen peroxide upon contact with an aqueouscomposition are provided in a first solid composition, and the firstsolid composition is contacted with a second aqueous composition to formperoxyformic acid in the resulting aqueous composition.

The resulting aqueous composition that comprises peroxyformic acid canbe any suitable types of aqueous compositions. For example, theresulting aqueous composition can be an aqueous solution. In anotherexample, the resulting aqueous composition can be an aqueous suspension.

Before the contacting step, the ratio between the concentration of theformic acid (w/v) and the concentration of the hydrogen peroxide (w/v)can be in any suitable range. In some embodiments, before thecontacting, the ratio between the concentration of the formic acid (w/v)and the concentration of the hydrogen peroxide (w/v) can be from about 2to about 100, e.g., about 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10,10-15, 15-20, 20-25, 25-30, 30-35, 35-40, 40-45 or 45-50 or greater fromabout 50-100.

The ratio between the concentration of the peracid (w/w) and theconcentration of hydrogen peroxide (w/w) in the formed aqueouscomposition can reach any suitable range. In some embodiments, the ratiobetween the concentration of the peracid (w/w) and the concentration ofhydrogen peroxide (w/w) in the formed aqueous composition can reach,within about 4 hours, or preferably 2 hours of the contacting, fromabout 2 to about 1,500, e.g., about 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9,9-10, 10-15, 15-20, 20-25, 25-30, 30-35, 35-40, 40-45, 45-50, 50-60,60-70, 70-80, 80-90, 90-100, 100-200, 200-300, 300-400, 400-500,500-600, 600-700, 700-800, 800-900, 900-1,000, 1,000-1,100, 1,100-1,200,1,200-1,300, 1,300-1,400, or 1,400-1,500. In other embodiments, theratio between the concentration of the peracid (w/w) and theconcentration of hydrogen peroxide (w/w) in the formed aqueouscomposition reaches at least about 10 within about 30 minutes of thecontacting, preferably at least about 10-40 within about 30 minutes ofthe contacting.

The formed aqueous composition can comprise any suitable concentrationof hydrogen peroxide. In some embodiments, the formed aqueouscomposition can comprise about 5% (w/w) or less hydrogen peroxide, e.g.,about 5% (w/w), 4.5% (w/w), 4% (w/w), 3.5% (w/w), 3% (w/w), 2.5% (w/w),2% (w/w), 1.5% (w/w), 1% (w/w), 0.9% (w/w), 0.8% (w/w), 0.7% (w/w), 0.6%(w/w), 0.5% (w/w), 0.4% (w/w), 0.3% (w/w), 0.2% (w/w), 0.1% (w/w), 0.05%(w/w), 0.01% (w/w), 0.005% (w/w), or 0.001% (w/w) of hydrogen peroxide.In other embodiments, the formed aqueous composition reaches about 2%(w/w) or less hydrogen peroxide within about 1 hour, or preferablywithin about 10 minutes of the contacting. In still other embodiments,the formed aqueous composition reaches about 1% (w/w) or less hydrogenperoxide within about 1 hour of the contacting. In yet otherembodiments, the formed aqueous composition reaches about 0% (w/w) toabout 0.001% (w/w) hydrogen peroxide and maintains about 0% (w/w) toabout 0.001% (w/w) hydrogen peroxide for about 1 hour.

In many aspects of the invention, a low hydrogen peroxide containingperoxyformic acid is desirable and unexpectedly provides benefits intreating membranes. In an embodiment, a low hydrogen peroxide containingperoxyformic acid does not cause damage to membranes, including underseawater treatment environments and overcomes a significant limitationof the state of the art. In a preferred aspect, the peroxyformic acidcompositions include non-equilibrium ratios of peroxyformic acid tohydrogen peroxide. In an aspect, the ratio of peroxyformic acid tohydrogen peroxide is at least 5:1, at least 10:1, at least 15:1, atleast 20:1, at least 25:1, at least 30:1, at least 35:1, or at least40:1. This is distinct from conventional peroxycarboxylic acids, such asperoxyacetic acid having a ratio of peroxycarboxylic acid to hydrogenperoxide of about 1:1 to about 1.5:1.

The formic acid and the hydrogen peroxide can be contacted in theabsence of a C₂-C₂₂ carboxylic acid and/or a C₂-C₂₂ percarboxylic acidand the peracid in the formed aqueous composition comprises peroxyformicacid only.

The formic acid and hydrogen peroxide can be contacted in the presenceof a C₂-C₂₂ carboxylic acid and the peracid in the formed aqueouscomposition comprises peroxyformic acid and the C₂-C₂₂ percarboxylicacid. Any suitable C₂-C₂₂ carboxylic acid can be used in the presentmethods. In some embodiments, the C₂-C₂₂ carboxylic acid is acetic acid,octanoic acid and/or sulfonated oleic acid, and the peracid in theformed aqueous composition comprises peroxyformic acid and one or moreof peroxyacetic acid, peroxyoctanoic acid and peroxysulfonated oleicacid.

The present methods can be conducted at any suitable temperature. Insome embodiments, the present methods can be conducted at a temperatureranging from about −2° C. to about 70° C., about 10° C. to about 70° C.,e.g., about 10° C.-15° C., 15° C.-20° C., 20° C.-25° C., 25° C.-30° C.,30° C.-35° C., 35° C.-40° C., 40° C.-45° C., 45° C.-50° C., 50° C.-55°C., 55° C.-60° C., 60° C.-65° C., or 65° C.-70° C. In other embodiments,the present methods can be conducted under ambient conditions. In stillother embodiments, the present methods can be conducted under heating,e.g., at a temperature ranging from about 30° C.-35° C., 35° C.-40° C.,40° C.-45° C., 45° C.-50° C., 50° C.-55° C., 55° C.-60° C., 60° C.-65°C., or 65° C.-70° C.

The present methods can be conducted in the presence of a catalyst. Anysuitable catalyst can be used in the present methods. In someembodiments, the catalyst can be a mineral acid, e.g., sulfuric acid,nitric acid, phosphoric acid, pyrophosphoric acid, polyphosphoric acid,or organic acids, such as methanesulfonic acid, xylene sulfonic acid,toluene sulfonic acid, phosphonic acids such as 1-hydroxyethane1,1-diphosphonic acid (HEDP)

The present methods can be conducted in the presence of a cation acidexchange resin system. Any suitable cation acid exchange resin systemcan be used in the present methods. In some embodiments, the cation acidexchange resin system is a strong cation acid exchange resin system. Inother embodiments, the acid exchange resin system is sulfonic acidexchange resin, e.g., commercially-available as Dowex M-31 or Nafion.

The formic acid provided in a first aqueous composition can be contactedwith the hydrogen peroxide provided in a second aqueous composition thatalso comprises peroxyacetic acid to form a resulting aqueous compositionthat comprises a total peracid that comprises peroxyformic acid andperoxyacetic acid. Before the contacting step, the ratio between theconcentration of the formic acid (w/v) and the concentration of thehydrogen peroxide (w/v) can be at any suitable range. The ratio betweenthe concentration of total peracid (w/w) and the concentration ofhydrogen peroxide (w/w) in the resulting aqueous composition can alsoreach any suitable range. In some embodiments, before the contacting,the ratio between the concentration of the formic acid (w/v) and theconcentration of the hydrogen peroxide (w/v) can be about 5 or higherand the ratio between the concentration of total peracid (w/w) and theconcentration of hydrogen peroxide (w/w) in the resulting aqueouscomposition reaches at least about 5 within about 2 minutes of thecontacting. In other embodiments, the ratio between the concentration oftotal peracid (w/w) and the concentration of hydrogen peroxide (w/w) inthe resulting aqueous composition can reach at least about 10 withinabout 20 minutes of the contacting. In yet other embodiments, before thecontacting, the ratio between the concentration of the formic acid (w/v)and the concentration of the hydrogen peroxide (w/v) can be about 20 orhigher and the ratio between the concentration of total peracid (w/w)and the concentration of hydrogen peroxide (w/w) in the resultingaqueous composition can reach at least about 10 within at least about 1minute of the contacting. The concentration of hydrogen peroxide (w/w)in the resulting aqueous composition can reach any suitableconcentration. In some embodiments, the concentration of hydrogenperoxide (w/w) in the resulting aqueous composition can reach about 0%(w/w) to about 0.001% (w/w) hydrogen peroxide within at least about 4hours, or preferably 2 hours of the contacting. In other embodiments,the concentration of hydrogen peroxide (w/w) in the resulting aqueouscomposition can remain at about 0% (w/w) to about 0.001% (w/w) for least1 hour. In other embodiments, the concentration of hydrogen peroxide inthe resulting aqueous composition can remain at about 0% to about 0.1%for least 10 min.

The resulting aqueous composition can comprise a stabilizing agent forthe peracid. Any suitable stabilizing agents can be used in the presentmethods. Exemplary stabilizing agents include a phosphonate salt(s)and/or a heterocyclic dicarboxylic acid, e.g., dipicolinic acid.

The present methods can further comprise a step of reducing theconcentration of the hydrogen peroxide in the resulting aqueouscomposition. The concentration of the hydrogen peroxide in the resultingaqueous composition can be reduced using any suitable methods. Forexample, the concentration of the hydrogen peroxide in the resultingaqueous composition can be reduced using a catalase or a peroxidase.

The resulting aqueous composition can comprise any suitableconcentration of peroxyformic acid. In some embodiments, the resultingaqueous composition comprises from about 0.00001% (w/w) to about 20%(w/w) peroxyformic acid, e.g., about 0.0001%-0.005% (w/w),0.0005%-0.010% (w/w), 0.001%-0.050% (w/w), 0.005%-0.1% (w/w), 0.01%-0.5%(w/w), 0.05%-1% (w/w), 1%-2% (w/w), 2%-3% (w/w), 3%-4% (w/w), 4%-5%(w/w), 5%-6% (w/w), 6%-7% (w/w), 7%-8% (w/w), 8%-9% (w/w), 9%-10% (w/w),10%-11% (w/w), 11%-12% (w/w), 12%-13% (w/w), 13%-14% (w/w), 14%-15%(w/w), 15%-16% (w/w), 16%-17% (w/w), 17%-18% (w/w), 18%-19% (w/w), or19%-20% (w/w) peroxyformic acid.

The present methods can be used to generate peroxyformic acid in anysuitable manner or at any suitable location. In some embodiments, thepresent methods can be used to generate peroxyformic acid in situ forthe application of the formed peroxyformic acid.

The peroxyformic acid formed using the present methods (presentcomposition) can further comprise other percarboxylic acids. A peracidincludes any compound of the formula R—(COOOH)_(n) in which R can behydrogen, alkyl, alkenyl, alkyne, acylic, alicyclic group, aryl,heteroaryl, or heterocyclic group, and n is 1, 2, or 3, and named byprefixing the parent acid with peroxy. Preferably R includes hydrogen,alkyl, or alkenyl. The terms “alkyl,” “alkenyl,” “alkyne,” “acylic,”“alicyclic group,” “aryl,” “heteroaryl,” and “heterocyclic group” are asdefined herein. Various embodiments of the invention referring toperoxyformic acid compositions and/or peroxyformic acid solutions arefurther understood to optionally comprise additional percarboxylicacids. As used herein, the term “peracid” may also be referred to as a“percarboxylic acid” or “peroxyacid.” Sulfoperoxycarboxylic acids,sulfonated peracids and sulfonated peroxycarboxylic acids are alsoincluded within the term “peracid” as used herein. The terms“sulfoperoxycarboxylic acid,” “sulfonated peracid,” or “sulfonatedperoxycarboxylic acid” refers to the peroxycarboxylic acid form of asulfonated carboxylic acid as disclosed in U.S. Patent Publication Nos.2010/0021557, 2010/0048730 and 2012/0052134 which are incorporatedherein by reference in their entireties. A peracid refers to an acidhaving the hydrogen of the hydroxyl group in carboxylic acid replaced bya hydroxy group. Oxidizing peracids may also be referred to herein asperoxycarboxylic acids.

In other embodiments, a mixed peracid is employed, such as aperoxycarboxylic acid including at least one peroxycarboxylic acid oflimited water solubility in which R includes alkyl of 5-22 carbon atomsand at least one water-soluble peroxycarboxylic acid in which R includesalkyl of 1-4 carbon atoms. For example, in one embodiment, aperoxycarboxylic acid includes peroxyacetic acid and at least one otherperoxycarboxylic acid such as those named above. Preferably acomposition of the invention includes peroxyformic acid, peroxyaceticacid and/or peroxyoctanoic acid. Other combinations of mixed peracidsare well suited for use in the current invention. Advantageously, acombination of peroxycarboxylic acids provides a composition withdesirable antimicrobial activity in the presence of high organic soilloads. The mixed peroxycarboxylic acid compositions often providesynergistic micro efficacy. Accordingly, compositions of the inventioncan include a peroxycarboxylic acid, or mixtures thereof.

Water

The peroxyformic acid compositions according to the invention maycomprise water in amounts that vary depending upon techniques forprocessing the composition. Water provides a medium which dissolves,suspends, or carries the other components of the composition. Water canalso function to deliver and wet the composition of the invention on anobject.

In some embodiments, water makes up a large portion of the compositionof the invention and may be the balance of the composition apart fromperoxyformic acid composition. The water amount and type will dependupon the nature of the composition as a whole, the environmentalstorage, and method of application including concentration composition,form of the composition, and intended method of delivery, among otherfactors. Notably the carrier should be chosen and used at aconcentration which does not inhibit the efficacy of the functionalcomponents in the composition of the invention for the intended use.

Additional Peroxy Acids

The peroxyformic acid compositions according to the invention maycomprise an additional peroxyacid. Any suitable C₁-C₂₂ percarboxylicacid can be used in the present compositions. In some embodiments, theC₁-C₂₂ percarboxylic acid is a C₂-C₂₀ percarboxylic acid. In otherembodiments, the C₁-C₂₂ percarboxylic is a C₁, C₂, C₃, C₄, C₅, C₆, C₇,C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅, C₁₆, C₁₇, C₁₈, C₁₉, C₂₀, C₂₁, orC₂₂ percarboxylic acid. In still other embodiments, the additionalC₁-C₂₂ percarboxylic acid comprises peroxyacetic acid, peroxyoctanoicacid and/or peroxysulfonated oleic acid.

The additional percarboxylic acid can be added to the peroxyformic acidin any suitable concentration. In some embodiments, the resultingaqueous composition comprises from about 0.00001% (w/w) to about 20%(w/w) peroxyformic acid, e.g., about 0.0001%-0.005% (w/w), 0.0005%-0.01%(w/w), 0.001%-0.05% (w/w), 0.005%-0.1% (w/w), 0.01%-0.5% (w/w), 0.05%-1%(w/w), 1%-2% (w/w), 2%-3% (w/w), 3%-4% (w/w), 4%-5% (w/w), 5%-6% (w/w),6%-7% (w/w), 7%-8% (w/w), 8%-9% (w/w), 9%-10% (w/w), 10%-11% (w/w),11%-12% (w/w), 12%-13% (w/w), 13%-14% (w/w), 14%-15% (w/w), 15%-16%(w/w), 16%-17% (w/w), 17%-18% (w/w), 18%-19% (w/w), or 19%-20% (w/w).

Additional Functional Ingredients

The components of the peroxyformic acid compositions can further becombined with various functional components suitable for use in membranetreatment. In some embodiments, the peroxyformic acid compositions makeup a large amount, or even substantially all of the treatmentcomposition for the membranes as disclosed herein. For example, in someembodiments few or no additional functional ingredients are disposedtherein.

In other embodiments, additional functional ingredients may be includedin the compositions. The functional ingredients provide desiredproperties and functionalities to the compositions. For the purpose ofthis application, the term “functional ingredient” includes a materialthat when dispersed or dissolved in a use and/or concentrate solution,such as an aqueous solution, provides a beneficial property in aparticular use. Some particular examples of functional materials arediscussed in more detail below, although the particular materialsdiscussed are given by way of example only, and that a broad variety ofother functional ingredients may be used.

In some embodiments, the peroxyformic acid compositions may includesurfactants, such as for example nonionic and anionic surfactants,defoaming agents, anti-redeposition agents, bleaching agents, solubilitymodifiers, dispersants, rinse aids, metal protecting agents, stabilizingagents, corrosion inhibitors, sequestrants and/or chelating agents,wetting agents, water conditioning agents or chelants, enzymes,fragrances and/or dyes, rheology modifiers or thickeners, hydrotropes orcouplers, buffers, acids and bases, mineral and organic acids, solventsand the like.

Builders

The present compositions or cleaning use solutions can include abuilder. Builders include chelating agents (chelators), sequesteringagents (sequestrants), and the like. The builder may act to stabilizethe cleaning composition or use solution. Examples of builders include,but are not limited to, phosphonates, phosphates, aminocarboxylates andtheir derivatives, pyrophosphates, polyphosphates, ethylenediamene andethylenetriamene derivatives, hydroxyacids, and mono-, di-, andtri-carboxylates and their corresponding acids. Other exemplary buildersinclude aluminosilicates, nitroloacetates and their derivatives, andmixtures thereof. Still other exemplary builders includeaminocarboxylates, including salts of ethylenediaminetetraacetic acid(EDTA), hydroxyethylenediaminetetraacetic acid (HEDTA), anddiethylenetriaminepentaacetic acid. For a further discussion ofchelating agents/sequestrants, see Kirk-Othmer, Encyclopedia of ChemicalTechnology, Third Edition, volume 5, pages 339-366 and volume 23, pages319-320, which is incorporated in its entirety. According to an aspectof the invention, preferred builders are water soluble, biodegradableand phosphorus-free. The amount of builder in the cleaning compositionor use solution, if present, is typically between about 10 ppm and about1000 ppm in the cleaning composition or use solution.

Acidulants and Catalysts

Acidulants may be included as additional functional ingredients in acomposition according to the invention. In an aspect, a strong mineralacid such as nitric acid, sulfuric acid, phosphoric acid or a strongerorganic acid such as methyl sulfonic acid (MSA) can be used. Thecombined use of a strong mineral acid or stronger organic acid with theperacid composition provides enhanced antimicrobial efficacy. Inaddition, some strong mineral and organic acids, such as nitric acid,provide a further benefit of reducing the risk of corrosion towardmetals contacted by the peracid compositions according to the invention.In some embodiments, the present composition does not comprise a mineralacid or a strong mineral acid.

In an aspect, the methods of forming the peroxyformic acid may beconducted in the presence of a catalyst. Any suitable catalyst can beused in the present methods. In some embodiments, the catalyst can be amineral or strong organic acid, e.g., sulfuric acid, nitric acid,phosphoric acid, pyrophosphoric acid, polyphosphoric acid. The catalystmay also be an organic acid, e.g., methanesulfonic acid, xylene sulfonicacid, toluene sulfonic acid, phosphonic acid such as HEDP. Suchcatalysts may be present in peroxyformic acid forming composition in anamount of at least about 0 wt-% to about 10 wt-%, preferably at leastabout 0.1 wt-% to about 5 wt-%, more preferably from about 1 wt-% toabout 5 wt-%.

Acidulants may be employed in amounts sufficient to provide the intendedantimicrobial efficacy and/or anticorrosion benefits. Such agents may bepresent in a use solution in an amount of at least about 0.1 wt-% toabout 10 wt-%, preferably at least about 0.1 wt-% to about 5 wt-%, morepreferably from about 0.1 wt-% to about 1 wt-%.

Surfactants

The surfactants described hereinabove can be used singly or incombination with the methods of the present invention. In particular,the nonionics and anionics can be used in combination. The semi-polarnonionic, cationic, amphoteric and zwitterionic surfactants can beemployed in combination with nonionics or anionics. The above examplesare merely specific illustrations of the numerous surfactants which canfind application within the scope of this invention. It should beunderstood that the selection of particular surfactants or combinationsof surfactants can be based on a number of factors includingcompatibility with the membrane at the intended use concentration andthe intended environmental conditions including temperature and pH.Accordingly, one should understand that surfactants that may damage aparticular membrane during conditions of use should not be used withthat membrane. It is expected that the same surfactant, however, may beuseful with other types of membranes. In addition, the level and degreeof foaming under the conditions of use and in subsequent recovery of thecomposition can be a factor for selecting particular surfactants andmixtures of surfactants. For example, in certain applications it may bedesirable to minimize foaming and, as a result, one would select asurfactant or mixture of surfactants that provides reduced foaming. Inaddition, it may be desirable to select a surfactant or a mixture ofsurfactants that exhibits a foam that breaks down relatively quickly sothat the composition can be recovered and reused with an acceptableamount of down time. In addition, the surfactant or mixture ofsurfactants can be selected depending upon the particular soil that isto be removed.

It should be understood that the compositions for use with the methodsof the present invention need not include a surfactant or a surfactantmixture, and can include other components. In addition, the compositionscan include a surfactant or surfactant mixture in combination with othercomponents. Exemplary additional components that can be provided withinthe compositions include builders, water conditioning agents,non-aqueous components, adjuvants, carriers, processing aids, enzymes,and pH adjusting agents. When surfactants are included in theperoxyformic acid compositions in a use solution they can be included inan amount of at least about 0.1 wt. % to about 10 wt. %.

Anionic Surfactants

The peroxyformic acid compositions can contain a surfactant component(s)that includes a detersive amount of an anionic surfactant or a mixtureof anionic surfactants. Anionic surfactants are desirable in cleaningcompositions because of their wetting, detersive properties, and oftentimes good compatibility with membranes. The anionic surfactants thatcan be used according to the invention include any anionic surfactantavailable in the cleaning industry. Suitable groups of anionicsurfactants include sulfonates and sulfates. Suitable surfactants thatcan be provided in the anionic surfactant component include alkyl arylsulfonates, secondary alkane sulfonates, alkyl methyl ester sulfonates,alpha olefin sulfonates, alkyl ether sulfates, alkyl sulfates, andalcohol sulfates. Suitable alkyl aryl sulfonates that can be used in thecleaning composition can have an alkyl group that contains 6 to 24carbon atoms and the aryl group can be at least one of benzene, toluene,and xylene. A suitable alkyl aryl sulfonate includes linear alkylbenzene sulfonate. A suitable linear alkyl benzene sulfonate includeslinear dodecyl benzyl sulfonate that can be provided as an acid that isneutralized to form the sulfonate. Additional suitable alkyl arylsulfonates include xylene sulfonate. Suitable alkane sulfonates that canbe used in the cleaning composition can have an alkane group having 6 to24 carbon atoms. Suitable alkane sulfonates that can be used includesecondary alkane sulfonates. A suitable secondary alkane sulfonateincludes sodium C14-C17 secondary alkyl sulfonate. Suitable alkyl methylester sulfonates that can be used in the cleaning composition includethose having an alkyl group containing 6 to 24 carbon atoms. Suitablealpha olefin sulfonates that can be used in the cleaning compositioninclude those having alpha olefin groups containing 6 to 24 carbonatoms. Suitable alkyl ether sulfates that can be used in the cleaningcomposition include those having between about 1 and about 10 repeatingalkoxy groups, between about 1 and about 5 repeating alkoxy groups. Ingeneral, the alkoxy group will contain between about 2 and about 4carbon atoms. A suitable alkoxy group is ethoxy. A suitable alkyl ethersulfate is sodium lauryl ether ethoxylate sulfate. Suitable alkylsulfates that can be used in the cleaning composition include thosehaving an alkyl group containing 6 to 24 carbon atoms. Suitable alkylsulfates include, but are not limited to, sodium lauryl sulfate andsodium lauryl/myristyl sulfate. Suitable alcohol sulfates that can beused in the cleaning composition include those having an alcohol groupcontaining about 6 to about 24 carbon atoms.

Further examples of suitable anionic surfactants are given in “SurfaceActive Agents and Detergents” (Vol. I and II by Schwartz, Perry andBerch). A variety of such surfactants are also generally disclosed inU.S. Pat. No. 3,929,678. The disclosures of the above referencesrelating to anionic surfactants are incorporated herein by reference.

Nonionic Surfactants

The peroxyformic acid compositions can contain a surfactant component(s)that includes a detersive amount of a nonionic surfactant or a mixtureof nonionic surfactants. Nonionic surfactants can be included in thecomposition to enhance soil removal properties. Nonionic surfactantsuseful in the invention are generally characterized by the presence ofan organic hydrophobic group and an organic hydrophilic group and aretypically produced by the condensation of an organic aliphatic, alkylaromatic or polyoxyalkylene hydrophobic compound with a hydrophilicalkaline oxide moiety which in common practice is ethylene oxide or apolyhydration product thereof, polyethylene glycol. Practically anyhydrophobic compound having a hydroxyl, carboxyl, amino, or amido groupwith a reactive hydrogen atom can be condensed with ethylene oxide, orits polyhydration adducts, or its mixtures with alkoxylenes such aspropylene oxide to form a nonionic surface-active agent. The length ofthe hydrophilic polyoxyalkylene moiety which is condensed with anyparticular hydrophobic compound can be readily adjusted to yield a waterdispersible or water-soluble compound having the desired degree ofbalance between hydrophilic and hydrophobic properties.

Nonionic surfactants that can be used in the composition includepolyalkylene oxide surfactants (also known as polyoxyalkylenesurfactants or polyalkylene glycol surfactants). Suitable polyalkyleneoxide surfactants include polyoxypropylene surfactants andpolyoxyethylene glycol surfactants. Suitable surfactants of this typeare synthetic organic polyoxypropylene (PO)-polyoxyethylene (EO) blockcopolymers. These surfactants include a di-block polymer comprising anEO block and a PO block, a center block of polyoxypropylene units (PO),and having blocks of polyoxyethylene grafted onto the polyoxypropyleneunit or a center block of EO with attached PO blocks. Further, thissurfactant can have further blocks of either polyoxyethylene orpolyoxypropylene in the molecules. A suitable average molecular weightrange of useful surfactants can be about 1,000 to about 40,000 and theweight percent content of ethylene oxide can be about 10-80 wt. %.

Additional nonionic surfactants include alcohol alkoxylates. An suitablealcohol alkoxylate include linear alcohol ethoxylates. Additionalalcohol alkoxylates include alkylphenol ethoxylates, branched alcoholethoxylates, secondary alcohol ethoxylates, castor oil ethoxylates,alkylamine ethoxylates, tallow amine ethoxylates, fatty acidethoxylates, sorbital oleate ethoxylates, end-capped ethoxylates, ormixtures thereof. Additional nonionic surfactants include amides such asfatty alkanolamides, alkyldiethanolamides, coconut diethanolamide,lauramide diethanolamide, cocoamide diethanolamide, polyethylene glycolcocoamide, oleic diethanolamide, or mixtures thereof. Additionalsuitable nonionic surfactants include polyalkoxylated aliphatic base,polyalkoxylated amide, glycol esters, glycerol esters, amine oxides,phosphate esters, alcohol phosphate, fatty triglycerides, fattytriglyceride esters, alkyl ether phosphate, alkyl esters, alkyl phenolethoxylate phosphate esters, alkyl polysaccharides, block copolymers,alkyl glucosides, or mixtures thereof.

Other exemplary nonionic surfactants for use with the methods of thepresent invention are disclosed in the treatise Nonionic Surfactants,edited by Schick, M. J., Vol. 1 of the Surfactant Science Series, MarcelDekker, Inc., New York, 1983, the contents of which is incorporated byreference herein. A typical listing of nonionic classes, and species ofthese surfactants, is also given in U.S. Pat. No. 3,929,678. Furtherexamples are given in “Surface Active Agents and Detergents” (Vol. I andII by Schwartz, Perry and Berch). The disclosures of these referencesrelating to nonionic surfactants are incorporated herein by reference.

Amphoteric Surfactants

Amphoteric surfactants can also be used to provide desired detersiveproperties. Amphoteric, or ampholytic, surfactants contain both a basicand an acidic hydrophilic group and an organic hydrophobic group. Theseionic entities may be any of anionic or cationic groups described hereinfor other types of surfactants. A basic nitrogen and an acidiccarboxylate group are the typical functional groups employed as thebasic and acidic hydrophilic groups. In a few surfactants, sulfonate,sulfate, phosphonate or phosphate provide the negative charge. Suitableamphoteric surfactants include, but are not limited to: sultaines,amphopropionates, amphodipropionates, aminopropionates,aminodipropionates, amphoacetates, amphodiacetates, andamphohydroxypropylsulfonates.

Amphoteric surfactants can be broadly described as derivatives ofaliphatic secondary and tertiary amines, in which the aliphatic radicalmay be straight chain or branched and wherein one of the aliphaticsubstituents contains from about 8 to 18 carbon atoms and one containsan anionic water solubilizing group, e.g., carboxy, sulfo, sulfato,phosphato, or phosphono. Amphoteric surfactants are subdivided into twomajor classes. The first class includes acyl/dialkyl ethylenediaminederivatives (e.g. 2-alkyl hydroxyethyl imidazoline derivatives) andtheir salts. The second class includes N-alkylamino acids and theirsalts. Some amphoteric surfactants can be envisioned as fitting intoboth classes.

Zwitterionic Surfactants

In some embodiments, zwitterionic surfactants are used with the methodsof the invention. Zwitterionic surfactants can be thought of as a subsetof the amphoteric surfactants. Zwitterionic surfactants can be broadlydescribed as derivatives of secondary and tertiary amines, derivativesof heterocyclic secondary and tertiary amines, or derivatives ofquaternary ammonium, quaternary phosphonium or tertiary sulfoniumcompounds. Typically, a zwitterionic surfactant includes a positivecharged quaternary ammonium or, in some cases, a sulfonium orphosphonium ion; a negative charged carboxyl group; and an alkyl group.Zwitterionics generally contain cationic and anionic groups which ionizeto a nearly equal degree in the isoelectric region of the molecule andwhich can develop strong “inner-salt” attraction betweenpositive-negative charge centers. Examples of such zwitterionicsynthetic surfactants include derivatives of aliphatic quaternaryammonium, phosphonium, and sulfonium compounds, in which the aliphaticradicals can be straight chain or branched, and wherein one of thealiphatic substituents contains from 8 to 18 carbon atoms and onecontains an anionic water solubilizing group, e.g., carboxy, sulfonate,sulfate, phosphate, or phosphonate. Betaine and sultaine surfactants areexemplary zwitterionic surfactants for use herein.

A typical listing of zwitterionic classes, and species of thesesurfactants, is given in U.S. Pat. No. 3,929,678. Further examples aregiven in “Surface Active Agents and Detergents” (Vol. I and II bySchwartz, Perry and Berch). The disclosures of zwitterionic surfactantsin the above references are incorporated herein by reference.

All publications and patent applications in this specification areindicative of the level of ordinary skill in the art to which thisinvention pertains. All publications and patent applications are hereinincorporated by reference to the same extent as if each individualpublication or patent application was specifically and individuallyindicated as incorporated by reference.

EXAMPLES

Embodiments of the present invention are further defined in thefollowing non-limiting Examples. It should be understood that theseExamples, while indicating certain embodiments of the invention, aregiven by way of illustration only. From the above discussion and theseExamples, one skilled in the art can ascertain the essentialcharacteristics of this invention, and without departing from the spiritand scope thereof, can make various changes and modifications of theembodiments of the invention to adapt it to various usages andconditions. Thus, various modifications of the embodiments of theinvention, in addition to those shown and described herein, will beapparent to those skilled in the art from the foregoing description.Such modifications are also intended to fall within the scope of theappended claims.

The materials used in the following Examples are provided herein:

Various commercially-available stock solutions were employed informulations (available from various sources) including: methanesulfonic acid (70%), linear alkylbenzene sulphonates (96%), sodiumxylene sulfonate (40%), formic acid (85%), and hydrogen peroxide (50%).

POAA: a commercial product containing 5.25 to 6.4% peroxyacetic acid and25.6 to 29.4% H₂O₂.

Exemplary peroxyformic acid compositions employed in the Examples arelisted in the Table 1 below:

TABLE 1 PFA-30-1 PFA-30-2 FA-30-3 Component (wt %) (wt %) (wt %) Water0.00 0.00 16.25 MSA (70%) 3.0 3.0 3.0 LAS (96%) 4.93 0 4.93 Formic acid(85%) 75.82 80.75 75.82 H₂O₂ (50%) 16.25 16.25 0 Total 100.00 100.00100.00 PFA (5 min after mixing) 10.19% 9.22% 0.00%

The peroxyformic acid compositions shown in Table 1 were made from atwo-part system. Part A provided the formic acid and optionally withother ingredients excluding the H₂O₂. Part B for the formulations PFA30-1 and PFA 30-2 provided H₂O₂ and optionally with other ingredientsexcluding the formic acid provided in Part A. On mixing Part A and PartB under ambient conditions, peroxyformic acid (PFA) reached maximumlevel within 5 min., i.e. the compositions were ready to use.Composition 30-3 is a formic acid composition and not a peroxyformicacid composition.

Accordingly, the peroxyformic acid formed provides a superior biocideagainst microorganisms, especially spores and biofilms suitable for theuses disclosed herein according to the embodiments of the invention.Moreover, the formic acid in the composition (as demonstrated byComposition 30-3) serves as an efficient proton source in dissolvingmineral scale build up on spiral bound membrane elements.

Example 1

The removal of biofilm was tested to determine efficacy of biofilmremoval and kill rates of Pseudomonas aeruginosa. Pseudomonas arewell-known as common ‘pioneer’ bacteria and often tested forbiofilm-inhibiting agents' effectiveness. The bacteria are known toexcrete polysaccharides and generate biofilm on a variety of surfacesvery rapidly (including, for example, membrane filtration elements), aswell as commonly demonstrate resistance to various antimicrobialcompositions. However, bacteria that exist in a biofilm arephenotypically different from suspended cells of the same genotype;therefore the study of biofilm in the laboratory requires protocols thataccount for this difference. Laboratory biofilms are engineered ingrowth reactors designed to produce a specific biofilm type. Alteringsystem parameters correspondingly results in a change in the biofilm.

Pseudomonas aeruginosa (ATCC 700888) was the organism used. An isolatedcolony was aseptically removed from an R2A plate and placed into 100 mlof sterile bacterial liquid growth broth (300 mg/L) and incubated in anenvironmental shaker at 35° C. for 20-24 hours. Viable bacterial densityshould equal 108 CFU/ml, and may be checked by serial dilution andplating. Pseudomonas aeruginosa were grown in a CDC reactor system for48 hours at room temperature. See Goeres, D. M., et al., Statisticalassessment of a laboratory method for growing biofilms, Microbiology151:757-762 (2005). Biofilm challenge is approximately 8 logs throughouttesting from a 48-hour growth.

Small Koch HFK-131 UF membrane rectangles were prepared by punching outa spiral wound membrane and placing the membrane disk into a plasticrectangle used to serve as “framing material”. The membranes were placedinto the CDC rod and used for testing.

After the biofilm was developed, the membrane rectangles were removedand placed into a sterile plastic centrifuge tube. Each exemplarycomposition was pipette into the centrifuge tube in duplicate andexposed to the membrane rectangles for the specified exposure time (5 or10 minutes) at room temperature. After the specified exposure time thesolutions were neutralized in Neutralizer Broth, vortexed, sonicated,serially diluted and plated for plate counts. The average log reductionfor each evaluated composition was obtained as follows: peroxyformicacid (Formulations 30-1 and 30-2), untreated control not containingperoxyformic acid (Formulation 30-3), and a commercially-availableantimicrobial composition (peroxyacetic acid composition). The resultsof these experiments are shown in FIG. 1.

As can be seen in FIG. 1, all three exemplary compositions efficientlyreduced Pseudomonas aeruginosa biofilm at the indicated exposure times.Compositions 30-1 and 30-2 at the concentration of 0.3% (product)provide significant log reduction in (>6.68) at both the 5 and 10-minuteexposure times, while the average log reduction for composition 30-3containing formic acid alone (4.15 at 5 minutes and 3.02 at 10 minutes)has significantly less efficacy against the test microorganism. At leasta 3-log reduction in the biofilm organisms is conventionally required asa commercial threshold for biofilm treatments to comply with EPArequirements. Accordingly, the PFA compositions according to theinvention provide suitable compositions for membrane treatment.

Accordingly, the peroxyformic acid formed provides a superior biocideagainst microorganisms, especially spores and biofilms suitable for theuses disclosed herein according to the embodiments of the invention.Moreover, the formic acid in the composition (as demonstrated byComposition 30-3) serves as an efficient proton source and providesbenefits to treating the membranes as well.

Example 2

In addition to biofilm disruption during membrane filtration, mineralscale also serves as a significant hindrance which reduces output anddecreases the life of the membrane filtration elements. Mitigation ofmineral buildup was tested to determine efficacy of the exemplarycompositions to solubilize excess minerals.

For these experiments, compositions 30-1 (0.3%), 30-2 (0.3%), and 30-3(0.3%) were prepared to be tested. Product dilutions were made in DIwater and the initial pH of the solution was recorded. The testdilutions are then added to a beaker and stirred at 25° C. Excessamounts of calcium mineral (either phosphate or carbonate solids) wereadded until the solution was opaque and the amount of mineral added isrecorded. The excess mineral is allowed to settle for about 5 minutesand a final pH of the acidic solutions are recorded. The solutions arethen filtered and standard ICP-MS methods are used to determine calciumand phosphorus solubility capacity in the various formulations. Theresults of these experiments are provided in Tables 2A and 2B belowwhich show the ability of the peroxyformic and formic acid compositionsto dissolve mineral deposits. As the scale removal capability isdependent on the amount of acid used in the composition, no control dataset is provided, instead the compositions 30-1 and 30-2 providingperoxyformic acid are compared with 30-3 providing formic acid.

TABLE 2A ~100 Ca₃(PO₄)₂ pH pH ICP Ca Formula g g Temp (initial) (final)ppm PFA-30-1 (0.3%) 100.6 0.50 25° C. 2.53 3.60 629 PFA-30-2 (0.3%)100.1 0.50 25° C. 2.52 3.94 964 Formic Acid 100.2 0.50 25° C. 2.49 3.61769 30-3 (0.3%)

TABLE 2B pH pH ICP Formula ~100 g CaCO₃ g Temp (initial) (final) Ca ppmPFA-30-1 (0.3%) 100.4 0.50 25° C. 2.55 5.53 943 PFA-30-2 (0.3%) 100.10.50 25° C. 2.53 5.97 1210 Formic Acid 99.9 0.50 25° C. 2.49 5.44 105030-3 (0.3%)

All three formulas were very efficient in solubilizing both calciumcarbonate and calcium phosphate. In general, an ICP Ca above 400 ppm isconsidered to display efficient solubilizing capacity which isindicative of the solubilizing of the minerals as required for cleaninga membrane. As can be seen in Tables 2A and 2B, formula 30-2 (0.3%)displays the highest solubility capacity of the formulas tested, whileformulas 30-1 and 30-3 show desirable solubility capacity as well. Asshown, the peroxyformic acid compositions provide desirable dissolvingof mineral scale build up, such as that which is found on membraneelements. The formic acid composition also provides an efficient protonsource in dissolving mineral scale build up, such as that which is foundon membrane elements. The results confirm that the use of theperoxyformic acid compositions and formic acid compositions are suitablereplacements for strong acid cleaning conventionally used in analternating fashion with an alkaline cleaning step for membranes.Instead, according to embodiments of the invention, the biocidalperoxyformic acid compositions and formic acid compositions can be usedin membrane cleaning to replace strong acids which are known to bedetrimental (noncompatible) with membranes.

Example 3

It is important that any possible formula used for membrane filtrationcleaning be compatible with the membranes and not impact membranefunction. To determine the membrane compatibility formula 30-1 (0.5%)was compared to POAA and DI water was used as a negative control.

Membranes are initially rinsed with DI water to remove residual storagebuffer and are placed in a 1 gallon jar. The test solutions are added tothe 1 gallon jar and placed in an oven at 50° C. for 24 hours. After 24hours, the test solution is removed and replaced with fresh testsolution. The jar is placed back in an oven for 24 hours and this sameprotocol is repeated 2 more times for a total of 4 days. Based Tables 3Aand 3B below 4 days is equivalent to 1.5 years of exposure for dailymembrane cleanings.

TABLE 3A Daily Application Wash Time 10 Min Washes/Week 7 WashesWeeks/Year 52 Weeks Exposure Time/Year 3640 min/year 1.5 Years TotalExposure 5460 Minutes Total Exposure 91 Hours Total Exposure 3.791667Days

TABLE 3B Weekly Application Wash Time 10 Min Washes/Week 1 washesWeeks/Year 52 Weeks Exposure Time/Year 520 min/year 1.5 Years TotalExposure 780 minutes Total Exposure 13 Hours Total Exposure 0.541667Days

After the 4 days exposure the membranes are rinsed with DI water andplaced on the Flat Sheet Membrane skid (Model M20). The membranes arerinsed with DI water for 24 hours at standard UF pressure andtemperature. Once 24 hours is completed the membranes are subjected toalkaline conditioning step until solution pH is 11. 15.14 grams of NaClis added to the recirculating water (2000 ppm NaCl) and the system isallowed to continue circulating. The conductivity of each permeate tubeand feed is then measured and recorded and shown as percent rejection.The percent rejection is determined by (conductivity of thefeed—conductivity of the permeate)/(conductivity of the feed). FIG. 3shows two different runs (Series 1 and Series 2) testing the membranecompatibility of 30-1 (0.5%) being compared with POAA (0.25% product)and DI water control.

On average a brand new (virgin) RO membrane will measure at least (>)97% rejection. This high percentage rejection refers to the percentageof permeate that is rejected, i.e. does not pass through the membrane.The higher the percentage, including above 97% rejection is a goodindicator that an experimental formula displays membrane compatibilityand does not damage the membrane. As can be seen in FIG. 3, all of theformulas evaluated have no impacts on the membranes comparing to watercontrol through a virgin RO membrane. Formula 30-1 (0.5%) displayed anaverage percent rejection comparable to POAA.

In combination, Examples 1-4 show the exemplary formulas of the presentinvention may be particularly useful as an anti-microbial wash todissolve mineral scale and kill biofilms while not decreasing the lifeof the membrane filtration elements. Indeed, the results shown in theabove examples demonstrates that the exemplary compositions are superioragainst microorganisms and are very efficient in dissolving mineralscale on the membranes, furthermore, the compositions, under theevaluated conditions have no impacts on the membranes comparing to watercontrol.

Example 4

The effects of PFA on reverse osmosis members which contain a poly-amidestructure in comparison with known control chemicals were tested. Threedifferent membranes were tested including Koch HRX, Hydranautics CPA5and Hydranautics ESPA2+. Membranes were soaked in duplicate, inchemistries according to Table 4.

TABLE 4 Chemistry Use Concentration None N/A Chlorine and NaOH 50 ppmChlorine at pH = 11 POAA 1100 ppm PFA  300 ppm

Membranes were then conditioned in Ultrasil 110 at a pH of 11 for 90minutes at 50° C., followed by a rinse in DI water. Membranes were thenprepared for testing according to Example 4 at the test conditions shownin Table 5.

TABLE 5 Chemistry Simulated Time Soak Time (hr) Temperature (F.) NoneN/A 0 77 Chlorine and 3 Years 936 122 NaOH POAA 3 Years 234 77 PFA 1Year 78 77 PFA 3 Years 234 77

Each of the chemistries, with the exception of PFA was refreshed daily.PFA was refreshed hourly. After the simulated exposure the membranes arerinsed with DI water and placed on the Flat Sheet Membrane skid (ModelM20). The membranes were rinsed with DI water for 24 hours at standardUF pressure and temperature. Once 24 hours was completed the membraneswere subjected to alkaline conditioning step until solution pH is 11.15.14 grams of NaCl was added to the recirculating water (2000 ppm NaCl)and the system was allowed to continue circulating. The conductivity ofeach permeate tube and feed was then measured and recorded and shown aspercent rejection. The percent rejection was determined by (conductivityof the feed−conductivity of the permeate)/(conductivity of the feed).

FIG. 4 demonstrates the results of clean water flux for the testedmembranes, while FIG. 5 depicts the salt rejection for each of thetested membranes. In combination, FIGS. 4-5 show the compatibility ofthe membranes with PFA. Table 6 proves the initial values for the fluxand the salt rejections. Tables 7-8 represent the numerical resultsshown in FIGS. 4-5.

TABLE 6 Initial Water Flux Initial Salt Rejection Membrane (LMH) (%)Koch HRX 40.08 95.73 Hydranautics 57.72 97.02 CPA5 Hydranautics 62.5396.58 ESPA2+

TABLE 7 Water Salt Rejec- Water Salt Rejec- Flux (LMH) tion (%) Flux(LMH) tion (%) Membrane POAA POAA Chlorine Chlorine Koch HRX 75.2293.88 * * Hydranautics 75.22 94.88 124.16 82.92 CPA5 Hydranautics 89.0396.40 138.31 84.02 ESPA2+

TABLE 8 Water Salt Rejec- Water Salt Rejec- Flux (LMH) tion (%) Flux(LMH) tion (%) Membrane PFA 1 YR PFA 1 YR PFA 3 YR PFA 3 YR Koch HRX65.40 91.26 75.84 87.50 Hydranautics 66.99 91.89 80.58 89.71 CPA5Hydranautics 86.13 93.50 96.38 93.01 ESPA2+

As shown, PFA at 300 ppm is more compatible with a RO membrane thanconventional chlorine treatment at 50 ppm and pH of 11. Membranesexposed for a simulated 1 year to PFA at 300 ppm provided comparableresults to that of the commercially-available control peroxyacetic acidcompositions at 3 years. Surprisingly, neither peroxyformic acid norformic acid under the levels used was reactive to the membranes treatedaccording to the embodiments of the invention. The demonstration of ROmembrane compatibility signifies the chemistry and methods of theinvention are suitable for the most sensitive of the membrane types(RO), indicating the compatibility for less sensitive (larger pore sizerange and filtration level) membranes, including microfiltration,ultrafiltration and nanofiltration. This is significant as the pore sizeof the membranes is the known factor of the membranes dictatingcompatibility (despite other differences in the membranes, including forexamples construction material, e.g. adhesives).

Example 5

Additional testing was performed to compare percent biofilm reductioncomparing glutaraldehyde and peroxyformic acid.

TABLE 9 Biofilm percent reductions Total biofilm Viable biofilm ATPGlutaraldehyde - 58% 81% 94% 250 ppm PFA-75 ppm active 85% 96% 99%As shown in Table 9 and FIG. 6, the biofilm volume in terms of totalbiofilm and viable biofilm is more effectively reduced according to thepresent invention when compared to traditional glutaraldehyde cleaningcomponents.

Example 6

The effectiveness of the present invention against a Pseudomonas biofilmin a continuous in-line simulation was also tested according to theconditions shown in Table 10. Concentration X time parameter was keptthe same for all concentrations tested: 25 ppm was treated for 60minutes, 50 ppm for 30 minutes, 100 ppm for 15 minutes, 100 ppm for 7.5minutes and 200 ppm for 3.7 minutes, respectively. The concentrationshere refer to the product concentration employed; for example the 100ppm peroxyformic acid composition is equivalent to 15 ppm PFA active.

TABLE 10 Concentration as product final Time Concentration x Flow Ratecomposition (min) Flow (mL/min) 400 3.75 1500 5 200 7.5 1500 5 100 151500 5 50 30 1500 5 25 60 1500 5Microbial concentration following treatment was collected and allconditions according the present invention provided superior microbialreduction in comparison with UT, a conventional cleaning protocol.

Example 7

As previously discussed, free chlorine concentration is a concern formembrane use and cleaning as excessive exposure to free chlorine canmake membranes prone to breakage due to oxidation. As such, it is anobject of the present invention to ensure that in presence of sourcewaters where are salinized or naturally salinized, i.e., sea water, thefree chlorine concentration does not increase to undesirable levels.

A DPD based assay was used to quantitate free chlorine in test samplesaccording to the present invention as well as2,2-dibromo-3-nitrilopropionamide (DBNPA), which is commonly used as aquick-kill biocide that easily hydrolyzes under both acidic and alkalineconditions. Replacement or reduction of the DBNPA is beneficial due toenvironmental concerns associated with the biocide. Free chlorineoxidizes DPD, changing the color from colorless to pink via use of aWüster dye. Further, the reaction is pH dependent. DPD and theappropriate buffer are packaged together in DPD Free Chlorine ReagentPower (Cat. No. 21978-46). Contents of the package were dissolved with 5mLs of deionized, high purity MilliQ water before use. Results are shownin FIGS. 7-8. As shown in FIG. 7, the presence of salt water creates aminor color change indicating the additional presence of salination doesnot substantially impact the free chlorine generation when compositionsaccording the present invention are employed. FIG. 8 depicts that whencomparing the present invention to that of DBNPA, the present inventionprovides substantially less free chlorine generation. The figures areshown in grey scale, with the darker color indicating a darker pinkcolor change according to the example.

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. The present disclosure is an exemplification of theprinciples of the invention and is not intended to limit the inventionto the particular embodiments illustrated. All patents, patentapplications, scientific papers, and any other referenced materialsmentioned herein are incorporated by reference in their entirety.Furthermore, the invention encompasses any possible combination of someor all of the various embodiments mentioned herein, described hereinand/or incorporated herein. In addition the invention encompasses anypossible combination that also specifically excludes any one or some ofthe various embodiments mentioned herein, described herein and/orincorporated herein.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the claims where the term“comprising” means “including, but not limited to”. Those familiar withthe art may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims.

What is claimed is:
 1. A method for removing microorganisms and mineraldeposits on a membrane system comprising: contacting the membrane fouledwith a hydrocarbon, biofilm, mineral scales, and/or iron sulfide with aperoxyformic acid composition, wherein the composition is membranecompatible and does not damage the membrane as measured by a decrease influx of the membrane; and removing microbial growth and dissolvingmineral deposits on the membrane.
 2. The method of claim 1, wherein themembrane is a reverse osmosis membrane, nanofiltration membrane,ultrafiltration membrane, or a microfiltration membrane.
 3. The methodof claim 1, wherein the membrane comprises cellulose, cellulose acetate,nitrocellulose, polysulfone, polyethersulfone, fully aromatic polyamide,polyvinylidene fluoride, polytetrafluoroethylene, polyacrylnitrile,polypropylene, carbon, alpha-aluminum oxide, zirconium oxide, ceramicand/or stainless steel.
 4. The method of claim 1, wherein the treatmentwith the peroxyformic acid composition does not negatively impact thepressure on the membrane and/or decrease the lifespan of the membrane incomparison to a membrane treated with other oxidizer chemistries.
 5. Themethod of claim 1, further comprising at least one additional step of afirst product removal step before the membrane is contacted with theperoxyformic acid composition, a pre-rinse step of washing the membranewith water, a soak step of washing the membrane, and/or an additionaltreatment cycle(s) comprising an acidic treatment, an enzymatictreatment, an alkaline treatment and/or a neutral treatment eitherbefore or after the peroxyformic acid composition contacts the membrane.6. The method of claim 1, wherein the membrane is contacted with fromabout 0.00001% to about 0.1% active peroxyformic acid.
 7. The method ofclaim 1, wherein the membrane is contacted with peroxyformic acid for atleast 15 minutes.
 8. The method of claim 1, wherein the membrane iscontacted with peroxyformic acid for at least 1 hour.
 9. The method ofclaim 1, wherein the membrane is contacted with an additionalperoxyacid, chelants, solvent, surfactant and/or other additives whichmay be dosed separately or simultaneously with the peroxyformic acidcomposition.
 10. The method of claim 1, wherein the membrane iscontacted with the peroxyformic acid composition at temperature rangefrom ambient temperature to about 60° C.
 11. The method of claim 1,wherein the peroxyformic acid composition is generated in situ bycontacting formic acid with hydrogen peroxide, wherein before saidcontacting, the ratio between the concentration of said formic acid(w/v) and the concentration of said hydrogen peroxide (w/v) is about 2or higher, and the ratio between the concentration of said peracid (w/w)and the concentration of hydrogen peroxide (w/w) in said formedresulting aqueous composition reaches about 2 or higher within about 1hour of said contacting.
 12. The method of claim 11, wherein the formicacid is provided in a first aqueous composition and is contacted with asecond aqueous solution of the hydrogen peroxide.
 13. The method ofclaim 11, wherein the contacting of the formic acid and hydrogenperoxide is conducted in the presence of an acid catalyst.
 14. Themethod of claim 1, wherein the peroxyformic acid composition comprises awetting agent, a chelant, solvent and/or a surfactant.
 15. The method ofclaim 1, wherein the ratio of the peroxyformic acid to the hydrogenperoxide in the peroxyformic acid composition is from about 10:1 toabout 40:1.
 16. The method of claim 1, wherein the ratio of theperoxyformic acid to the hydrogen peroxide in the peroxyformic acidcomposition is from about 25:1 to about 40:1.
 17. The method of claim 1,which further comprises a step of reducing the concentration of thehydrogen peroxide in the peroxyformic acid composition.
 18. The methodof claim 1, wherein contacting the membrane with at least about 1 ppm toabout 300 ppm actives of peroxyformic acid composition.
 19. The methodof claim 1, wherein contacting the membrane with at least about 1 ppm toabout 200 ppm actives of peroxyformic acid composition.
 20. A method forremoving microbial growth and mineral deposits on a membrane systemcomprising: contacting the membrane with at least about 1 ppm to about300 ppm actives of peroxyformic acid composition generated in situ; andremoving microorganisms mineral deposits on the membrane.